Optimal haptic control of a redundant 3-RRR Spherical Parallel Manipulator

This paper discusses an optimal torque distribution for a redundant 3-RRR spherical parallel manipulator (SPM). The SPM has parallel singular configurations within its workspace. The singularity leads to an amplification of the actuated joint torques which violates the actuator torque limits. The use of a redundant actuator solves the effect of the singularity. The quadratic sum of the actuated joint torques is minimized in order to obtain an optimal torque distribution. Experiments carried out show the advantage of introducing redundancy of actuators to improve the behavior of the SPM.